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Table of Contents Acknowledgement ....................................................................................................... iii Abstract ................................................................................................................. iv Table of Contents ......................................................................................................... vi List of Figures ............................................................................................................ xiii List of Tables ........................................................................................................... xviii Nomenclature ............................................................................................................ xxi Chapter 1 Introduction ............................................................................................... 1 1.1 Background ................................................................................................... 1 1.2 OSA Treatments ............................................................................................ 2 1.2.1 Oral Appliances ..................................................................................... 2 1.2.2 Surgeries ............................................................................................... 3 1.2.3 Breathing-Assistance Devices ................................................................ 4 1.3 Literature survey ........................................................................................... 7 1.3.1 Delivered air quality and the problem of condensation when using CPAP .............................................................................................................. 7 1.3.1.1 CPAP pressure consideration ............................................................ 7 1.3.1.2 Carbon dioxide limit in inhaled air .................................................... 7 1.3.1.3 Humidity and temperature of inhaled air ............................................ 7 1.3.1.4 Condensation in tube and its undesirability ........................................ 8 1.3.2 Former models....................................................................................... 8 1.4 Objectives ..................................................................................................... 9 Chapter 2 Mathematical Modelling of Fluid Dynamics ............................................ 11 2.1 Introduction ................................................................................................. 11 2.2 System overview ......................................................................................... 12 2.3 Fluid dynamic analysis ................................................................................ 13 2.3.1 Conduit internal flow and container mass balance analyses ................. 13 2.3.1.1 Internal flow analysis ....................................................................... 13 2.3.1.2 Mass balance ................................................................................... 15 2.3.2 Air Delivery Unit ................................................................................. 15 2.3.3 Connecting Duct .................................................................................. 20 2.3.4 Chamber air space mass balance ......................................................... 23 2.3.5 Heated Air Delivery Tube .................................................................... 24 2.3.6 Mask air mass balance ......................................................................... 25 2.4 Reverse flow and air transportation .............................................................. 29 vi
2.4.1 Reverse flow calculation ...................................................................... 29 2.4.2 Varying transport delay analysis .......................................................... 29 2.4.3 The effect of flow direction on air property transportation .................. 30 2.5 Exhaled air re-breathing .............................................................................. 32 2.6 Closure of the fluid dynamic mathematical modelling ................................. 34 Chapter 3 Mathematical Modelling of Thermodynamic Section ............................... 35 3.1 Introduction ................................................................................................. 35 3.2 Airflow in ADU .......................................................................................... 35 3.3 Chamber water heat balance ........................................................................ 40 3.3.1 Heat flow from the heating element to water ........................................ 44 3.3.1.1 Chamber base upper surface temperature ........................................ 44 3.3.1.2 Heat balance at the outer surface of the heating plate ...................... 47 3.3.2 Heat flow from chamber water into ambient air via wall 1, QC1i .......... 49 3.3.3 Heat transfer from the chamber water into chamber air wa Q ............... 50 3.3.4 Heat lost from the chamber water into chamber air by evaporationQev 53 3.4 Chamber-air heat balance ............................................................................ 55 3.4.1 Governing equation ............................................................................. 56 3.4.2 Heat carried into chamber air by evaporated molecules ...................... 56 3.4.3 Thermal energy brought in at the chamber inlet ................................... 57 3.4.4 Thermal energy at the outlet ................................................................ 57 3.4.5 Heat storage in chamber air ................................................................ 57 3.4.6 Heat transfer from chamber air into ambient via wall 2 and 3 ............. 58 3.4.6.1 Mixed convectional thermal resistance R C 23i .................................... 59 3.4.6.2 The conductive thermal resistance through the chamber wall 2 and 3 .. ........................................................................................................ 59 3.4.6.3 The thermal resistance at outer surfaces of wall 2 and 3 .................. 60 3.5 HADT heat balance ..................................................................................... 61 3.5.1 Heat energy brought in and out by inlet and outlet ............................... 62 3.5.2 Convection at HADT lump inner surface .............................................. 63 3.5.3 Convection at HADT lump outer surface .............................................. 63 3.5.4 Radiation at HADT outer surface ......................................................... 64 3.5.5 Heat storage in air of the lump............................................................. 65 3.6 HADT wall inner surface condensation analysis .......................................... 66 3.6.1 General comparison of condensation and evaporation ......................... 66 3.6.2 Condensation within the HADT............................................................ 67 3.7 Mask heat balance ....................................................................................... 69 vii
Page 1 and 2: The Effects of CPAP Tube Reverse Fl
Page 3 and 4: Acknowledgement First of all, I wou
Page 5: When deep breathing induced reverse
Page 9 and 10: 5.3.1 Thermal dynamic model under s
Page 11 and 12: XI.3 Steady state mask thermal bala
Page 13 and 14: List of Figures Figure 1.1 Obstruct
Page 15 and 16: Figure 5.10 Comparison between expe
Page 17 and 18: Figure 6.13 Fluctuation of airflow
Page 19 and 20: Table 5.3 Comparison of condensatio
Page 21 and 22: Nomenclature Symbol Meaning of the
Page 23 and 24: CMFeO CMFet C O C t Concentration o
Page 25 and 26: m C 23 m Ca m cv m Cw m store m i m
Page 27 and 28: Nu Cp Nu dir Nu Ti Nu To Nuwsn Nuws
Page 29 and 30: QMor QMwst QTastn QTicn QTin Q
Page 31 and 32: R Mic R Moc R Ticn R Toc R Torn Mas
Page 33 and 34: V Capacity of the container m 3 V C
Page 35 and 36: 1.1 Background Chapter 1 Introducti
Page 37 and 38: The MRD is worn in user’s mouth w
Page 39 and 40: Figure 1.4 CPAP machine Figure 1.5
Page 41 and 42: 1.3 Literature survey A literature
Page 43 and 44: CPAP fluid dynamic performance with
Page 45 and 46: Chapter 2 Mathematical Modelling of
Page 47 and 48: 2.3 Fluid dynamic analysis This sec
Page 49 and 50: If there are minor pressure drops,
Page 51 and 52: Figure 2.6 Pressure sensor - Honeyw
Page 53 and 54: The pressure readings were taken af
Page 55 and 56: Figure 2.12 Experimental set up for
Page 57 and 58:
2.3.4 Chamber air space mass balanc
Page 59 and 60:
From the above analysis, the pressu
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Figure 2.18 Full face mask and the
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Inserting Eq. (2.26) and Eq. (2.27)
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Where n( ) t is the airflow proper
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However in reality, mixing turns ou
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Chapter 3 Mathematical Modelling of
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An Environment Control Chamber (Vö
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Figure 3.4 Thermal enthalpy gain of
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Figure 3.6 Heating element beneath
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Figure 3.8 Chamber water heat balan
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Table 3.1 Thermal resistance from h
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3.3.1.2 Heat balance at the outer s
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3.3.2 Heat flow from chamber water
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through ADU which is a function of
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It is assumed that the direct impac
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Sc a a (3.47) Dwa Analogous to th
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and keep them in gaseous status. On
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through the walls and natural conve
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Where d Ca is the specific humidity
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TTa ( n1) is also considered as inl
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R Torn 2 2 ATlor ( TTWn T )( TTWn
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condensation severity but cannot ca
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condensation has occurred at all or
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The inlet is the air from HADT duri
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3.9 Average temperature of inhaled
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Table 4.1 Inputs to the fluid dynam
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Figure 4.2 Simulink TM model for fl
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Table 4.4 Outputs from the overall
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Gain block after input 1 is to conv
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Figure 4.7 Varying Transport Delay
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4.2.5 Mask mixing calculation subsy
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4.3 Computational model of thermal
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Figure 4.11 Block diagram of CPAP t
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Figure 4.13 Simulink TM model for t
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The outputs are listed in Table 4.1
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Figure 4.16 Dynamic chamber-air the
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Figure 4.17 HADT lump thermal balan
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Figure 4.18 Steady state HADT lump
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Figure 4.19 HADT lump air dynamic f
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Figure 4.21Steady state mask full t
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4 Temperature of airflow from HADT
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Average evaporation rate subsystem
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HADT and connects those upstream se
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The experiment was also carried out
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air flowing through the elbow, a ce
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expansion from the elbow to the mas
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Figure 5.12 Environmental control r
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Table 5.1 shows the combinations of
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Figure 5.17 Comparison of model out
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The comparison of experimental resu
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5.3.1.4 Airflow temperature at the
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flow rate had been even further inc
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Figure 5.31 Comparison of condensat
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Table 5.3 Comparison of condensatio
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3. The corrugated grooves on the HA
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5.3.2.1 Validation of evaporation r
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The experiment observation showed t
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Figure 6.1 Reverse flow under diffe
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It can also be seen in Figure 6.2 t
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within the same period. However, wh
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Figure 6.6 Comparison of evaporatio
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Figure 6.8 Airflow velocity in HADT
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Figure 6.11 Airflow velocity in HAD
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In Figure 6.14 the blue curve repre
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6.3.3.1.2 Comparison when heating e
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This vaporization potentiality (coi
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Figure 6.20 In-tube condensation of
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When using different sized masks, t
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Figure 6.23 Average specific humidi
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The average specific humidity in an
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Table 6.5 Comparison of average spe
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6. The deep breathing and reverse f
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Appendices Appendix I Regression of
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Appendix I. Regression of the press
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Figure I. 1 Tested results and the
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Appendix II. Regression of the pres
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Table III. 2 Airflow temperature an
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Appendix IV. The corrugated HADT ou
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The total area of the complicated c
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Figure V. 1 Regression of saturated
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This ratio can be regressed against
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Appendix VII. Details of the CPAP f
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VII.4 The mask pressure subsystem F
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Inputs to this water-centred subsys
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Input port number Input Unit 1 Heat
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input 4 is the portion of impact ar
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VIII.2.3 Water surface mass transfe
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This subsystem also contains two su
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VIII.2.5 Chamber wall 1 heat transf
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Figure VIII. 13 Wall 1 outer surfac
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Wall 2 and 3 inner surface temperat
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Figure VIII. 17 Chamber wall 2 and
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Inputs to this subsystem are listed
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Appendix IX. Details of steady stat
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Figure IX. 3 The HADT lump wall out
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Appendix X. Details of HADT lump ai
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2 Absolute value of airflow velocit
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Figure X. 5 HADT lump inlet absolut
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Figure XI. 2 Steady state mask mixi
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Figure XI. 4 Steady state mask wall
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Input port number Input Unit 1 Aver
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Appendix XII. Details of mask air d
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4 Length of the triangular plate in
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8 Length of the triangular plate in
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Appendix XIII. Details of the auxil
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XIII.3 Breath load average subsyste
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Figure XIII. 7 Average evaporation
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XIV.1.2 Under normal ambient temper
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XIV.2.3 Under high ambient temperat
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XIV.4 Airflow temperature at the en
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XIV.5.2 Under normal ambient temper
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XIV.6.3 Under high ambient temperat
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Appendix XVI. Regression of kinetic
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Figure XVII. 2 Condensation/evapora
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Figure XVIII. 2 Condensation/evapor
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at point C. Right after that, here
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Appendix XIX. Coefficient and param
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Average water thermal conductivity
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Appendix XXI. Fluid dynamic and the
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The lung simulator drives the air.
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Appendix XXII. Model user instructi
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The input blocks and their values a
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Dynamically fluctuating air tempera
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References [1] Good sleep advice. W
Page 315 and 316:
[28] Schettino GPP, Chatmongkolchar
Page 317:
[60] Marek R, Straub J. Analysis of
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